You can have a content area in a block yes.

So you can have blocks in blocks etc.

I would think once or twice before using it though.

It can make life for editors tricky. I prefer to keep my blocks without contentareas for this reason.

Do you ahve any example code that can show how this is done?

I imagine that for your scenario it would be better to create Parallax page type with single ContentArea. Then you put Blocks as rows in it. You do not need blocks to have ContentArea. 

Here is an article about how to create ContentArea rendering as rows:

http://blog.huilaaja.net/2015/09/14/episerver-content-area-renderer-with-row-support/

For adding an ContentArea to a page you can check out

http://geta.no/blogg/content-area---under-the-hood-part-i/

I was interested in Jon D Jones Parallax attempt - http://jondjones.com/jondjones-parallax-episerver-sample-site/#comment-6199- but Im getting this error:

No default Instance is registered and cannot be automatically determined for type ‘XXX.ContentRepository.IContentRepositoryFactory’

There is no configuration specified for XXX.ContentRepository.IContentRepositoryFactory

1.) new EpiServerDependencies(*Default of IContentRepositoryFactory*, *Default of ILinkResolverFactory*, *Default of IContextResolverFactory*)
2.) XXX.Dependencies.EpiServerDependencies
3.) Instance of XXX.Dependencies.EpiServerDependencies
4.) Container.GetInstance(XXX.Dependencies.EpiServerDependencies)

Do you know why this is – am I missing something?

I have only just seen this.  You need to include the structor map dependencies in your project.  Look in App_Code/StructureMapSetUp.cs